Genetic links of magmatic deposits in the Emeishan large igneous province with the dynamics of a mantle plume

Abstract

The Emeishan large igneous province in the western Yangtze Block was resulted from a mantle plume at end of the Middle Permian. Four super-large V-Ti-magnetite deposits and 10 large-medium Ni-Cu-(PGE) sulfide deposits have been explored in the Emeishan large igneous province. Precise age data indicated that these ore-bearing mafic-ultramafic intrusions were produced by the same mantle plume that caused the Emeishan flood basalts at 260 Ma±. The maficultramafic intrusion hosting V-Ti-magnetite deposits and Ni-Cu-(PGE) sulfide deposits are distinguished in localization, scale, rock-assemblages, components of rock-forming minerals. The Emeishan large province can be divided to Inner- and Outer-Zones. The Inner-Zone is marked by large thickness of the Emeishan flood basalts, large layered intrusions, mafic-ultrmafic intrusive bodies, low-Ti basalts, alkaline intrusions, and various mineralizations related to the mantle plume. The basalts become thinner and consist of high-Ti basalts in the Outer-Zone where fewer mafic-ultramafic bodies are exposed. Special and geochemical relationship between the two type of magmatic deposits and high- and low-Ti basalts,the study on petrogenetic links between the Ni-Cu-(PGE) sulfide deposits and the Emeishan flood basalts in the Yangliuping area indicate that the magmatic deposits formed in different dynamic stages of the mantle plume. The V-Ti-magnetite deposits are associated with the high-Ti basaltic magmas and related to fractional crystallization. In contrast, the Ni-Cu-(PGE) sulfide mineralization may be related to either the high- or low-Ti basaltic magmas and controlled by three factors: high degree partial melting of upper mantle, contamination of the lower crust, and fractional crystallization. The Ni-Cu-(PGE) sulfide deposits were formed earlier than the V-Ti-magnetite deposits.